The present invention relates to a burner for combusting a gas or liquid fuel to warm rooms, and dry and heat objects.
Known burners for producing high heat radiation include Schwank burners and catalytic combustion burners. Generally, the Schwank burners are widely used for obtaining heat radiation. However, the Schwank burners are disadvantageous in that their heat radiation ratio is limited and they are incapable of adjusting the amount of combustion due primarily to back fire. To prevent the back fire from occurring, the Schwank burner system includes a combustion body having combustion holes of extremely small diameter for enabling an air-fuel mixture to flow therein at a speed higher than the rate of combustion of the air-fuel mixture in the combustion holes. Therefore, the flame is normally generated downstream of the combustion body in the direction in which the air-fuel mixture flows. If the speed of flow of the air-fuel mixture were reduced below the combustion rate, then the flame would go upstream to result in a backfire. Thus, it would be difficult to change the speed of flow of the air-fuel mixture, and hence to change the amount of combustion. Since the flame is produced downstream of the combustion body at all times, the heat of combustion is not sufficiently transmitted to the combustion body, but discharged as waste heat. This is the reason why the heat radiation ratio of the Schwank burner system is limited to a low level ranging from about 30 to 40%.
The catalytic combustion burner has been developed in recent years to solve the problems of the Schwank burner. The general arrangement of the catalytic combustion burner is similar to that of the Schwank burner, except that a combustion catalyst is supported by the combustion body which is composed of a nonwoven fabric made of heat-resistant fibers such as of alumina. The air-fuel mixture supplied to the combustion body is burned at a relatively low temperature in the presence of the catalyst. Since the fuel is burned at a low temperature, backfires are less liable to take place and the amount of combustion can therefore be varied. As the fuel is combusted in the combustion body in its entirety, the combustion body is well heated by the heat of combustion so that the heat radiation ratio can be increased up to about 50%. Nevertheless, the Schwank burners still find wider use in domestic and industrial fields than the catalytic combustion burners because the cost performance of the catalytic combustion burners is low for the reasons that the attained increase in the heat radiation ratio is not good considering the cost of the expensive catalyst used and the range in which the amount of combustion can be varied is not large.